Pressure vessels are commonly used for containing a variety of fluids under pressure, such as hydrogen, oxygen, natural gas, nitrogen, propane, methane and other fuels, for example. Generally, pressure vessels can be of any size or configuration. The vessels can be heavy or light, single-use (e.g., disposable), reusable, subjected to high pressures (greater than 50 psi, for example), low pressures (less than 50 psi, for example), or used for storing fluids at elevated or cryogenic temperatures, for example.
Suitable pressure vessel shell materials include metals, such as steel; or composites, which may be formed of laminated layers of wound fiberglass filaments or other synthetic filaments bonded together by a thermo-setting or thermoplastic resin, for example. Composite construction of the vessels provides numerous advantages such as lightness in weight and resistance to corrosion, fatigue and catastrophic failure. These attributes are due at least in part to the high specific strengths of the reinforcing fibers or filaments that are typically oriented in the direction of the principal forces in the construction of composite pressure vessels.
A liner or bladder is often disposed within a composite pressure vessel shell to serve as a fluid permeation barrier, thereby sealing the vessel. Such a liner is often formed form a non-metallic, resilient material and prevents internal fluids from contacting the composite material.
Pressure vessels are subject to damage during transportation and use due to, for example, collision with other objects or being dropped. The ability of a vessel to retain a fluid at a desired pressure may be compromised by such damage. An existing approach to damage mitigation is to adhere a protective cap to an end of the vessel. However, caps that are merely adhered to the vessel may become dislodged during vessel use. Other approaches include increasing the shell thickness, applying elastomer shell coatings, and adding protective layers or end caps that are fully covered or encapsulated by additional shell material, as described in U.S. Pat. No. 5,476,189, discussed further below, and hereby incorporated by reference. Because the additional coatings or layers generally fully cover a damage-mitigating piece or the entire vessel, these approaches have the disadvantage of significantly increased material usage and manufacturing complexity.